No vegetables put down roots long enough to reach anything from the septic system. Go for it! Even if you have a back-up the plants will probably love it unless it sits too long.

Thanks for that. I've been trying to get as much input on this as I can find and so far it's been pretty much what you said. Mine will be the only front yard veg garden in my neighborhood. I'm not going to cover the whole yard and I'll put effort into the overall appearance, so hopefully the neighbors will be ok with it. As for the backyard, I'm seriously thinking about building a hen house and getting 4-6 laying hens, no roosters. Grocery prices are bad and will only get worse, so what the heck. Again, thanks for your input.

if you're really worried about it, dig down a couple of feet, and put a plastic liner in.

I planted some peas on my drain field this year an they did great an so far no problems. The way I looked at it grass roots are more permanent than annual veggies so surely it would be ok. I'm still picking peas.

Have you thought about raised beds with a plastic liner? There are some who worry about chemical or pathogenic contamination of the soil. We are contemplating that option for next spring.

Adding to my above post:
Our raised beds would be wide spaced and small, so as not to inhibit evaporation of moisture.

Someone elsewhere suggested container gardening, which seems like a good alternative and one we are exploring.